As Jennifer said but a bit added on: Remember R.I.C.E, Rest, Ice, Compression, Elevation. Make sure you don't rush back into rugby or running, it needs to be perfect because if it isn't perfectly fine, if you injure it again it'll be 100x worse. So I recommend not training/playing for a good couple of weeks. I know that is really not what you want to happen but it is the right thing to do

I find that microwavable heat packs (the wheat ones) are good for things like that. That's what I do when I pull muscles playing rugby, I find those the best as an ice pack doesn't really make a difference for something like that.

Ice elevate and rest. If its reallly painful u should go docs I hope u didn't tear ur ACL