Small round lump by ankle where thin bone from toes meet. it is firm no pain. what is it?

Most likely cyst: You may have a cyst , ganglion (less likely) , nodule or some benign process. If it is chronic , not changing in size or causing any pain or functional impairment ( mobility ) , you can watch it . Most likely it is just a harmless lump.

Mass Unknown Foot: You definitely want to have someone check any masses of unknown origin (like dropping something on your foot). Sometimes these are ganglions, but they are soft normally. Could be a bone spur with soft tissue coverage needing an xray to diagnosis. I would start with an evaluation and xray to be safe and go from there. Dr rich blake.

Get checked: Any lump should be check. It may be nothing or could be potential serious. I bet its nothing be safe not sorry.