My wife and I got certified in Cozumel 2 months ago. After we finished our certification, we did a few shore dives and a couple boat dives. At the end of the last boat dive, I had a little blood in my mask. Was a small amount and my nose did not continue to bleed. Was just woundering what may have caused this? I dont remeber any equalization problems during any dives and I didnt feel like I had any kind of sickness causing blocks/reverse blocks. Any ideas? Could I have had a cold that caused this problem and didnt even know it? Thanks