I was experimenting in ways to masturbate,(not gay)
And well I decided blowjob myself as I am that flexible and so I was giving myself a blowjob and I accidentally Bit my penis head and left a mark, shows when not erected but erected it doesn't show, So I was most likely wondering If I have some kind of disease, No puss came out no nothing leaked out, It doesn't burn unless touched by my hands. The marks are red.

Its been healing for 3 days and it looks like its almost gone and was wondering what I should do.

Do nothing!

Don't try your self-blowjob experiment again. It can only end badly.

Other then that, this in time shall heal.