What do i have on my skin, and can i treat it?

okay, i just went camping for 2 weeks. what i have on my body is what looks like a bug bite, but im not sure. at first it just itched a little, but then it got big and began to hurt. it is about an inch in wide and discolored and broozed. it still has the bite on top and bleeds and spews puss every once and a while. it hurts really really bad when i put pressure on it or try to walk (cuase it is on my leg) my whole family has it. can you please tell me what it might be and how to treat it, the sooner the better becuase it hurts like hell