Skyrim - Companions attacked me for no reason?

So, I was using Eorland Gray-Manes forge without causing any harm and all of a sudden I see loads of red dots on my map and it was the Companions and then even Eorland started attacking me. The Guards didn't do anything but cheered: "A Fight!" I even saw Vignar Gray-Mane attack me too. I have a bounty but it wasn't in Whiterun.

In general, most factions will not be hostile towards their own members. Adding yourself to the offending faction is often a solution to this kind of problem (e.g. Missing In Action, I've personally experienced that bug). The Companions have a faction ID of 00048362, so running this command should stop them attacking:

player.addtofaction 48362 0

This may break the quest Take Up Arms, and possibly the entire Companions questline with it. You should be able to resolve this by using setstage C00 <stage number> to partially or entirely skip the quest. It may be safer to skip one stage at a time instead of trying to skip the whole quest at once. It's also possible the quest will "just work" (or that it will work once you've advanced it to stage 10), so you should try to complete it normally first.

This does leave you a member of the Companions, which you may not have wanted, but you are not obligated to continue the questline, and membership in the Companions is rather useful in the early game, IMO. At a minimum, it gives you some free items, a place to sleep, and an endless supply of simple radiant quests.