I am pretty sure that this is sperm plug, but I don't want to hurt my cham so...
Do you think this is a sperm plug?
If yes, then i should soak it in some water and try to gently pull it out right?
Yes. Spermplug. You can gently pull it (won't hurt the Cham if you are careful), don't need water or anything else - or just leave it. It will go away naturally.
Mine had black dry stuff out and I pulled it out slowly as I was concerned for his health and turned out to be sperm plug. Glad I pulled it out, it was the right instinct