I have noticed 3 small open sores in my arm pit.. they are a little bit sore and have bled and pussed a little what could they be?

Folliculitis: You many have cut yourself shaving and then gotten an infection of a hair follicle which looks like a type of pimple called a pustule. Stop shaving until the area has healed and then use shaving cream before you shave. If it does not get better you ned to see a dermatologist for a topical antibiotic for your armpits. Throw out the blade from the razor, it may be contaminated with bacteria.

Lot's there: That area has a lot of things in it including arteries, veins, lymph nodes, etc. The skin however has a lot of sweat glands that have a risk of infection. Also, the many hair follicles there can also get infected. You need to be careful about keeping that area clean, minimize deodorant use as it can clog the pores. Right now, an antibiotic is probably needed, see a doc.