A couple of weeks ago, I tried to bleed for the first time my Shimano disc brake. I won't say it was easy and I'm not sure I did it perfectly but the fact it brakes better now.
However, I've noticed this morning that some mineral oil is leaking from the bleed nipple of the caliper. I noticed that I'd lost the cap. I also checked the bleed screw was correctly closed which is the case.
Is the bleed nipple cap essential and should I get a new one to avoid further leak? Would it be possible the leak have another origin?
For information, my caliper is a Shimano SM-MA-F180P/P2.