My 3-year-old got her flu shot today and

I'll start by checking what records already exist and which cards apply.

Nothing about the gym class or the park is a problem. If she is playing, drinking and chatty, that is the best sign there is — let her play at whatever pace her sore arm allows, and let tomorrow's preschool happen as normal.

I don't diagnose and I don't change or calculate any medicine dose, so what follows is routine and comfort care only.

1) What you tried vs. what works better

• Icing the arm: a fine, harmless comfort measure. Keep going if it soothes her. A cool damp cloth over the site works the same way. Neither replaces watching how she behaves overall.
• The bigger lever is the thermometer, not the ice. Check and write down her temperature and the time, so "the shot" and "whatever she picked up at the park" stay separable — and so you have real numbers if you end up calling anyone.
• Acetaminophen in the house: if you decide she is uncomfortable and you use it, follow the bottle's own instructions and her weight, not her age or the number on another child's bottle. I won't give you a dose. If it doesn't sit right, your pharmacist is the right person to ask.
• The free things that carry the evening: fluids, ordinary food she already likes, an earlier wind-down, and a lighter bedtime. None of these need buying or measuring.

2) What to avoid tonight

• Don't plan a "rest day" for her that she doesn't need — quiet watchfulness costs more than it buys, and she'll feel fine tomorrow.
• Don't give a second fever medicine on top of the first one because the number hasn't moved yet; check the labels for repeated ingredients.
• Don't skip tomorrow's preschool over a sore arm, and don't skip her next vaccination because of this one reaction.
• Don't chase a temperature on a schedule. One or two checks with times written down is enough for tonight.
• Don't let "the shot did this" swallow the rest: a cough, a vomiting episode or a rash that arrives in the next few days may well be an ordinary toddler illness, not the vaccine.

3) Decision tree — screenshot this

• Is she breathing comfortably, lips/tongue not swelling, no widespread hives, no wheeze, no collapse? → Yes: home routine. No: call your local emergency number now.
• Is she hard to wake, not drinking, floppy or unusually unresponsive? → Same-day clinic or urgent care, do not wait for tomorrow.
• Is the rash purple/red dots that do not fade when you press a glass on them, or is she having a fit? → Emergency now.
• Is the temperature high, or she is miserable and not settling, and it is not easing over the next day or two? → See a clinician; a vaccine reaction is a reasonable question, but an exam is how you rule out the other things.
• Is the arm just red, warm and tender, maybe a hard lump, but she is eating, drinking and playing? → This is the expected kind. Comfort, cool cloth, and let it be.

What success looks like in 24 hours: she drinks normally, plays or goes to preschool, maybe a tender arm, maybe one low reading on the thermometer, and a normal-ish night. That is a normal post-shot day, not a problem. I can't promise the sore arm disappears on a schedule, but the trend is what counts, not the number.

On your third question: yes — routine vaccination of toddlers is the norm in most countries' programmes, and that is exactly why the diseases these shots prevent are now rare where coverage is high. Which particular shots are due for a 3-year-old, and at what age, is your local programme's call, not mine: her clinic record and your national child-health programme are the two places that can answer it today. I won't hand you a month-by-month calendar from another country.

One thing to keep on the fridge: the vaccination card they gave you at the clinic, plus the clinic's phone number and after-hours line. If anything in the tree above sends you to a door, take the card and your two thermometer readings with you.

What I can't do: tell you whether this is normal *for her specifically*, or how long her reaction will last — that needs someone who can examine her. And if you tell me which country or city you're in, I can point you at the right local service numbers rather than guessing.