A week ago i noticed what i thought was a small boil on my leg but now is really big, red,hard to touch. no head. looks like a bite. what should i do?

Abscess: This could be now an abscess and might need to be opened under local anesthesia. Have it looked at by your primary care physician for evaluation and treatment.

Boil or bite: You should have a physician examine you for diagnosis and treatment. Boils and insect bites are often treated differently. If it's truly a boil and is larger, redder, tense and tender, it may need to be drained or at least aggressively treated with warm applications to bring it to a head. Bites may need antihistamines and antibiotic if complicated by cellulitis.