If it's just a fall from the lip to the substrate in a 10 gallon, I wouldn't be too worried...now if it were a 29 gallon or something taller...maybe.

Do you have a "soft" substrate like aspen? Maybe try one of those bendy branch things you can get to give him more ways up and down?
Short of affixing something to the lip to make it inaccessible, you probably won't get him to stop..."bad snake!" doesn't usually work