If you are still concerned, give him a good warm soak for an hour or two while you change out his cage conditions to maintain a higher humidity. By the time he comes out of the bath you should see some improvement. Put him in his nice, new, moist cage and he should be fine by the next day or two. If the dent is still there in a week, double check your cage conditions.
If you are having a hard time keeping the humidity up in the entire cage (common problem), try providing a Humid Hide. I just use an extra large tupperware container with a hole cut in the side, put down a thick layer of moist cypress mulch, a wet towel, or other moist substrate. Set it on the warm side and the snake can choose if it needs to be moist or not.
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25 year old 0.1 from Lincoln, NE
Ball Pythons - 0.1 Pastel, 1.0 Pastel het Pied, 0.1 Pied, 0.1 Cinn, 1.0 Black Pewter, 1.0 Woma (hidden gene?), 0.1 Yellowbelly, 2.1 Normals
Kingsnakes - 1.0 L. m. thayeri, 0.1 L. m. thayeri X L. alterna, 1.0 L. g. californiae
Other - 0.1 Whitesided P. catenifer sayi, 1.0 H. nascicus, ?.? Chrysemys picta, 0.1 crazy cat, 1.0 husband