I had a really bad nose bleed with a large clot. Then 2 hours later had another one. Haven't had any more in 48 hours. What could be the cause!

Need more info. The majority of nosebleeds do not require work-up or intervention. You do, however, need to seek professional care if they are frequent, long-lasting, you take blood thinners or you get lightheaded or have chest pain during/after one. During a nosebleed, make sure to pinch the soft part of the nose hard for 10 minutes- no peeking. If you keep bleeding after this, get to an ENT or er.
If recurs see ENT. You most likely have an area in the front of your nose that is inflamed and irritated. There are large superficial blood vessels in the front of the nose that are easily injured by blowing and cleaning. Seeing an ENT doctor is important as he/she can look in your nose and see if there is a vessel that can be easily cauterized. For now avoid putting anything in your nose including saline.