I need your help, kind of freaking out!

jd05ic

Hi. I had my first baby just over 5 months ago and was left with what i call "extreme stretch marks". Theyre extremely deep lines of saggy skin anywhere a person can get stretch marks. This morning i noticed a huge blister/boil thing has developed on a particularly bad stretch mark on my upper thigh (bikini line). It only hurts when I poke/prod it. Im really worried because it appeared so suddenly. Any ideas on what it could be or what i should do?