It sounds like you have improperly fitting shoes. And the "bruise" under your toe nail may be a blister from the friction of your toes rubbing against the toe box of your shoe. Numb toes can also be attributed to ill fitting shoes.
I would go to a proper running store (not a Macys, Sports Authority or any big name store like that) and get fit for a correct shoe for your foot and gait. That alone will make a world of difference. You may even asking the person fitting your shoe if you should go up a 1/2 size. That works wonders for some people.
Any burning you feel on your foot while exercising is what I call a "hot spot" and if left untreated will turn into a blister. When I'm exercising and feel hot spots, I stop, take off my shoes, and apply a band aid or blister pad to the hot spot area.
Also, I use Body Glide on my feet before going for a long walk. Body Glide helps reduce friction and helps prevent blisters. You can also try wearing a footie stocking under your socks while exercising. The stocking acts as a barrier between your foot and stock to help prevent friction.
I just completed the Breast Cancer 3-Day 60 mile walk and with proper foot care I didn't get a single blister and walked all 60 miles with happy feet. Taking care of your feet with proper shoes and anti-friction measures will allow you to walk for extended durations pain-free.