Son has 3in red hot circle with dot in the middle. Think its a bite. What do I do? He was bittin last night. The red very hot circle has me very concerned. What do I do? I put cortizone (hydrocortisone) 10 on it.

Tick Bite? Have it checked to ensure that it is not erythema chronicum migrans. This refers to the rash often (though not always) seen in the early stage of lyme disease. It can appear anywhere from one day to one month after a tick bite.
Rash. If you are really concerned than the only answer is to have a doctor look at it, even if it means going into an urgent care. First thing is to call his pediatricians office and ask the pediatrician who is on-call to please call you back to discuss first.
Cortizone (hydrocortisone) . Cortizone (hydrocortisone) 10 is fine for the inflammation associated with the itch, redness and swelling of a bug bite. Taking an oral antihistamine such as Diphenhydramine (benadryl) or loratidine (claritin) can also help. If the redness is worsening and is becoming painful, the bite may be infected. You can start by keeping the area clean with soap and water and applying antibiotic ointment to the bite. You can also try warm compresses to draw out the infection - 20 minutes (or as long as he lets you) 2-3 times a day. A warm bath works also. If the area has spreading redness, is worsening instead of improving or if your child develops fevers and chills, these are reasons to contact his doctor since he might need antibiotics to fight the infection.