First Injury

Just got back from my first 5 mile run with 4 miles being my previous best distance and had no soreness or pain during the run (apart from the usual 'can we stop now please' from my legs after about the first half mile!). But on getting home and and taking my shoes off I was rather alarmed to find bloodstains around my little toe on both socks. When I took the socks off there was a smaller amount of blood than I first though but it was dry and smeared around my 4th and little toe on both feet, I cleaned it up but couldn't find any cuts and since then I've had no further bleeding. Crucially I cut my toenails yesterday, maybe a little shorter than normal so I would be surprised if this wasn't something to do with it.

Looking at the bigger picture I wonder if my shoes are too small, I'm wearing size 10s just as I do the rest of the time but with insoles, running socks and the effect of 40-50 minutes non stop (and longer in future I would hope) perhaps my feet just don't have enough room?

I'd really appreciate the opinions of more experienced and more learned runners as I'm still very much a novice. I was on a high after reaching a new distance but then came down rather quickly when I got home