Slight trigger warning for unwanted private part pictures

I’m new so I’m not sure where this one should be posted but here we go

slight trigger warning for unwanted private part pictures

So a while back like 4 years ago or so this guy from my first year of high school (I’m now in my first year of collage) started sending me these messages wich this person ended up saying they where very horny and he was hard and wanted to send me a picture of his genitals I already started to feel uncomfortable by him saying he was horny and I said that to him but he kept sending me these messages on the same day and he said “do you want to see my penis because you made me really horny” and before I could say anything he send me a picture of his genitalia keep in mind I was like 12 and my mind just somehow keeps bribing it up out of no where and then I just feel dirty and want to cry and I don’t know what to do about it and I just needed to get this off of my chest and I just don’t know what to do about this anymore the picture is literally imprinted in my brain (I’m 17 now) and I can’t get it out of my head I want it gone I don’t know what to do all I can do is whenever I think about it is cry, panic/panic attack, scrub in the shower till I feel somewhat clean