Capsulitis. Most commonly you may have a capsulitis condition where the metatarsalphalangeal joints are inflamed, or you can have a mild bone bruise of one or more of the metatarsal bones. There are also other conditions that are not as common. You can try rest, ice, and some otc Ibuprofen or aleve (naproxen). If it doesn't improve, you should see a podiartist.
Capsulitis, stress. Capsulitis or stress fracture. Get an x-ray...If itg has been there for a while.