From my own life experience, I would say play with the idea that you may be bi. If you realize you're straight, cool, and if you realize you're bi, also cool. Worst that can happen is that you find out you don't like something new. But you can also find out there's a whole new aspect of dating and relationships that you might enjoy that you were previously unaware of. I've dated guys and girls and figured out I like both but prefer women. Honestly it hasn't affected my life that much in comparison to all the other things I live through. Society makes a huge deal about sexuality when it really doesn't matter that much. Only thing to consider is safety. If you live somewhere homophobic or have homophobic people in your life, just be careful about how much you vocalize. You can also talk to your friend who just came out. I've had a lot of queer friends and I can confidently say, telling your gay friend that you're questioning is something that he can really help you out with. Or asking other LGBT people on the internet or other friends you don't think there would be any tension on your relationship for asking. Maybe don't tell your friend you had thoughts about him specifically until you figure out yourself a little more. Regardless of what you end up identifying as, you deserve love and support. In the grand scheme of things, who we choose to love is really not that big of a deal. As long as you and your future partners are happy and you're not hurting anyone (including yourself), go for it! Humans aren't necessarily straight by nature, we're pretty flexible. At least that's what I've learned through my primate research. You might find out you still like girls after all and the thought was just a coincidence. You might find out you like both. You might find out you prefer men. It's honestly pretty fun to slowly figure out what things you like. I'm not saying immediately go out and fuck your friend, start with what you're comfortable with and just see how your brain reacts. Maybe that means doing nothing differently and keeping an open mind, maybe that means experimenting with more videos, maybe that means listening to other's life experience and finding out what resonates with you. But in my experience, trying to repress thoughts that aren't all that comfortable does nothing but hurt you. It's your life, choose to explore or not, but there's no benefit in judging your thoughts before they even happen. Good luck and remember to care for yourself first. You don't need to initiate an identity crisis now if you're not doing well already. Been there lol
Accepting the thoughts is your best plan of action. Intrusive thoughts will intrude, so don't treat this new one too special. That's how it traps you. You're doing great.