This is common
In most instances, it is because the toe nail is a little too long.
It usually occurs on the longest toe, probably your second toe. If the nail is a little long, it hits the end of the shoe at "toe-off". This causes the nail to wiggle a little on the nail bed, the soft tissue under the nail. After many cycles, that can cause tissue damage & bleeding under the nail. The fix = trim your toenails.