Open wound on Cats paw

My cat came home today around 6 hours ago with a wound on his upper paw, next to his 5th paw pad (the one on the back of the paw). Rinsed it with warm salt water at the time and as it was painful he didn't really let me inspect it properly. I've just come back from work and he's less lively than usual, was wondering if it requires urgent assistance or if he should be taken to the vets on Monday when they open. Looking like he probably does need to get taken to the vets, but if not I'd be grateful to know if there's anything that can be done at home to help the healing.

*Extra info* The wound is about 1cm wide right under the paw pad, inside layer of skin visible on the sides. Wasn't much bleeding at the start, none now. Looks like there could be a slight swelling but it's not massive.

Hello   Is there any chance that this could be a bite wound (eg dog / other cat)?  Bite wounds can be quite nasty as teeth are generally infected (covered in lots of bacteria) and effectively 'inject' those bacteria into a deep wound, causing deep infection that can then travel to the bloodstream.  Those wounds usually start off small and gradually swell from underneath as infection (or pus) accumulates.  The cat usually starts off fine and becomes lethargic as the site swells and their temperature rises.  Most cases are treated successfully.  However, a variety of causes exist that would answer your description - this was just the first example I thought of - and as a general rule, when unexplained lethargy is involved, we would advise calling your emergency vet for phone triage (an assessment so that the vet can figure out what the possibilities are and therefore how soon you need to be seen).

Other possibilities may include a 'pulled claw' (torn dew-claw) after getting caught somewhere, or a slash from vegetation or a foreign body, for example.  Wishing you the best of luck and please let us know how you get on.