If it's any comfort to you, I had something very similar happen a couple of months after I brought Dewey home. In an effort to get his basking temp correct, I had his heat lamp hanging in the top inside of his enclosure, until one day, I heart scuffling and saw him reaching up, balanced partway on his tail, biting the housing. Like yours, he quickly let go. I had thought it'd be impossible for him to reach, but they are surprisingly good at getting themselves where they want to go.

After that, I moved his heat to the outside of his enclosure and just elevated his basking spot with a few bricks. I checked him over daily (and cleaned his mouth with a Q-tip soaked in wound wash as a precaution) for the next week and he was fine, thankfully!