a mole that fell off

i am pretty worried. i have a mole for many years on my gluteal region. it was always brown with even color and borders . today i noticed a red symetrical red rim around the mole, the mole itself dident grow or changed its color but it became crusted . it dident itch bled or oozed when i tuchd it, but after a few scrathes it just fell off.. the mole after being scraped off looked like an old coagualted wound and was even in color. i was tested routinely less then 2 years ago by a dermatologist who found nothing suspected. should i be worried ? could this be due to trauma ?would be happy to get a reply soon

i also forgot to mention that after i scrathed it ,the surface that remianed bled.

i will for sure go to my doctor, i just wanted to know if i should be worried. the mole changed suddenly and now the surfacfe that is left looks like a red open wound and is a bit infalmmed and burns.is the sudden change a good sign?i was walking in the past week with really tight pants so i thought that should be the cause of the trauma