My 3 year old has a mosquito bites she scratched it and made pus come out. i cleaned and covered it..when to seek medical attention and it seem fine?

Now: If you see pus, this means infection. Your little one may have impetigo--easily treated with oral antibiotics and local area care. Please see MD.

Abscess = Infection: Kids commonly develop abscesses at the site of mosquito or ant bites. This is because bacteria on the skin is "auto-inoculated" into the fresh wound with scratching. If the wound is small or seems to be resolving, monitor and move on. But watch out! If pus keeps draining or there is a spreading area of redness, she needs to be evaluated! The wound may need drainage or oral antibiotics. Be safe!

Prob skin infection: Staph skin infections ( MRSA) are frequent and scratching a broken skin can certainly cause it. You should seek medical attention if any more pus bump appear or the skin becomes red or painful, when antibiotic treatment may be needed. Sometimes, bleach baths ( half cup of household bleach in half full bath tub) are helpful to reduce frequency if such skin infections