hey hun
You need to trust your gut feeling on what to do next. If the behaviour appears aggressive I would try dividing the cage if you can, if you feel they are on the verge of a proper fight. If it appears to be building into something worse and you can't divide their living quarters (so they can see each other but not hurt each other) then you may need to pop one in another cage or carrier over night so no one gets hurt. If you do this, please re-introduce on neutral territory, give them some time, monitor the behaviour. Then clean the cage so it's neutral smelling. You could also try a bonding bath, this experience will mean they smell the same and also they go through it together. Another trick is a teeny tiny dab of vick vapor rub on both bums. Again its all about smelling the same, the different scents are what sets off the territorial behaviour.
I had to seperate a pair of mine last year, i kept them apart for about 3 days simply until the weekend when I would have the time to bathe them and re-bond them. It worked for me and at the same time they had their cage upgraded to a 4x2 c & c cage, space is key with boars.
Sometime boys nip and bite noses when they're having a 'nose off'. Basically they reach higher and higher to see who will be highest and equally 'top pig'. It can happen accidentally if they're too close and catch each other with teeth. If they're no blood shed I would perservere, it can look scary but to them this is normal behaviour, establishing the heirachy, who's boss. If you haven't already, then ensure they have a food bowl each, water bottle each and their own bed/hidey places. It just limits the oppotunity for arguments. The best advice I was given when I had a problem was to commit to the situation , let them work through it, it often passes and again, only seperate if there is blood loss or bullying, like not letting the other eat.
How big is their current cage? it may be they just need more space

Hope this helps!