This blister looks like what they call a boil. should i continue to put alcohol on it? what kind of infection could it be?

See a doctor: It sounds like you have a skin infection and should see a doctor.

If it is an : Established infection under the skin surface, topical applications would not help. Incision and drainage of pus is the best option. You might also need systemic antibiotics. Skin infections are most commonly caused by staph, but other bacteria are possible. Go and see a doctor.