He trotted in this evening for his tea and his face is a right old mess. Fur ripped from his cheek and a gash. :rolleyes:

Its clean and I have just cleaned it up properly. Its not bothering him in the slightest (ate his tea and settled down in his favourite corner of the sofa).

Should I just keep an eye on it.

aahh poor thing, if its clean and not bothering him then I shouldn`t worry too much, just keep an eye on it, if it starts weeping pus or swelling then should get it looked at.
How deep is the cut?

I would say he's likely to get soem sort of infection - depends if it's claws or teeth, to a great degree, taht did the damage.

If it's a bite, then I'd say an infection is quite likely.

Keep an eye on it; when one of mine got clobbered like this years ago I only found the abcess from an infected bite when I stroked him and it burst on my fingers. Hadn't bothered him at all!

I whipped him down to the vets and all was well.

Best of luck!