Clear liquid came out of a small mole

I have a small mole on my arm that one day became slightly raised, i dont know if i caused it to do that, and as squeezed it clear liquid came out, i then picked it off and it heald into normal skin, before coming back the same size but darker. its pretty small and i know only a dermatologist can really tell me but can you help me and just tell me if this is always a serious thing.