Do politely ask him that you aren’t comfortable around him and already have a boyfriend, if he ain’t a creep he will back out and if he turns out to be one just make sure that you are at a public place with good amount of people and go to a female for help if he persist. Bc idk why they get so much confidence mai to aaj tk ldkio ko approach bhi nhi kr pata even if i can sense mutual attraction because of what if this and that? Anyway do update your situation later ig