Bubble/cyst/??? on penis - please help!

Basic info: * male * 26 years old * not sexually active * uncircumcised I've had this 'bubble' of sorts on the underside of my penis since my teens, as far as I remember. It's not painful. I can squeeze down on it and the bubble just shifts either up or down. It looks like it extends from my frenulem? I'm feeling insecure about it as I think it looks unsightly & abnormal. Any help appreciated - thank you! Images:

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