The only way to get the figures off their "mounts" is to cut them off. Use a sharp hobby knife (like an X-Acto) and BE CAREFUL!!! Make sure your fingers are not in the direction of your cutting.
MM's advice was good, too. Leave them on their bases and just cover them up with your groundwork.
In either case, BE CAREFUL!!
And did you take care of that gash? We wouldn't want it to get infected!