Metatarsalgia is a general term used to describe pain or discomfort in the forefoot around the area of the metatarsal heads (ball of the foot area), however discomfort in this area can usually be attributed to a specific condition.
Many in growing nails can be managed routinely with regular skilled cutting by the Podiatrist but some more acute cases may require the removal of the problematic part of the nail under a local anaesthetic, again the Podiatrist will be able to do this for you.
There is no difference between a Chiropodist and a Podiatrist, the term Podiatrist is just the more modern name for the same discipline.