What could cause the sensation of warm water in my right leg when its not exposed to any liquid?

Neurological. If you don't have any skin changes (redness/discoloration), the area is not tender to touch, and there are no new lumps or bumps, then this is most likely due to a neurological condition. Neurologists are best at evaluating this and will most likely recommend getting an MRI to look for any changes in the nerves.