i am torn between friendship and relationship, what to do?

So, yes we're all 18 in this story,
i have this really good male friend of mine, lets say M, he is very supportive and helps with studies, sometimes we study together, my boyfriend, has never had any issues, he too has female friends he studies with and we're very chill about this part, no complains regarding this in past 1.5 year of our relationship,

so the thing is, M and i are really close, he's a very good friend to me, my bf knows it and he's chill about it, in october, M confesses he likes me kind of and asks me to block him everywhere, and i did and told everything to my bf, from then M and i haven't talked,

now i meet M again and everything is veryy normal, he doesn't flirt or anything, and we're just like before, childhood bro's kinda, and my bf says he's chill with it unless M crosses any boundary..

i genuinely enjoy my time with M, but i am just worried about it ever going down with my bf, what if he one day blames me and accuses me of "entertaining" him despite there is nothing to be worried of

just my dilemma