I Notice Some Water Bubble Under My Penis Head. Any Advice On This ?

hi, i recently pulled back my penis foreskin about 2days back. after pulling back the foreskin i could see the penis head in a normal shape however it is very sensitive. i went out the next day and when i went to the toilet, i notice there is a strange bubble which appears to have liquid inside it forming under the penis head. the size has remain the same for the past 24hours. any advice on this? i am getting worried. i did not masturbate in the last 3days or have sex...so i am not sure what is the reason for the bubble to form under the penis head. is this normal? what should i do? any advice on this? thanks in advance. Cheers, Edmund