Painful, swelling blister

Hello! I have a question that I am pretty much concerned about. I'm not sure if it's a blister or something else. Apparently, I've developed a bump on my body and I thought it was a blister. But as the time pass, the bump started feeling like it was swelling and it became painful to the touch. It had broke open a few times and only dot of blood came out. I am having so much trouble moving around because of this since it's basically giving pain when I do. My question is that is it an infection or something else? And since I haven't been to the doctor in a long time, I'm also asking if the problem is treatable at home.