I have this weird bump on my leg, what could it be?

so i have this bump on my leg, its been there as long as i remember, you can press it and it almost feels as if its just air, however im sure thats not it. Its almost undetectable just by looking at it but you can definitely feel it. its not red, and theres not itching or any kind of pain. any idea of what this is?
Update: its not a pimple nor is it my kneecap as some have suggested, im 100% sure of that
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