Is it a risk?

i had one night sex with unkown girl she had a lot of red dots and pimples on her shoulder, biceps and back i kissed her boobs sucking and protected sex am i at the risk of hiv?

She may have just had an issue with acne? I get acne on my shoulders and back, and I do not have HIV.
I think you may be overthinking it, but if you’re concerned please just go get an STD screening done, as you should before/after any new partners.

ok understood
but what are the chances of transmission of HIV virus in a protected sex ?

very low.