My cat developed a small blister on one of his front toe pads. Its a dark red color with a small black dot in the middle leading me to believe he stepped on something. He is limping around on his other 3 legs since he will hardly even put his affected paw down other than to eat, drink, or jump up on something. For now I put a protective coating over it so he wont lick it and im keeping him in my room mostly so he doesn't further get injured. He is also a bit of an outdoor cat, he will go out for a few hours once or twice a day if he so desires. (as long as it's not raining or to cold. I wont let him out if that is the case) Then he will come back when I call him again. I wont leave him out at night either so he's a day time outdoor cat. I feel like he stepped on or swatted at something outside. The blister formed in less than a day. It's difficult to get him to the nearest vet at the moment so im hoping there is something I can do.
The main thing is to prevent any infection happening. I agree that it sounds like he stepped on something or landed on something when jumping down. Make sure you clean the wound thoroughly with an antibacterial soap, then apply an antibiotic ointment such as Neosporin to the wound. Wrap securely, but not too tightly, and check it frequently for any changes that might indicate an infection starting.
If an infection occurs then I suggest you get him to a vet to get it resolved. However, you might have caught it early enough that it will hopefully heal quickly. I wish you good luck with his healing.
A couple of pages that give some information on paws: