Dear friend,
I assume your boy has Lymphoma, here is info:
http://www.marvistavet.com/html/feline_lymphoma.html
The nosebleed is called epistaxis:
http://www.marvistavet.com/html/body_epistaxis__the_bloody_nose.html
As long as it has stopped it is not serious.
I hope your boy does well.
Best wishes for him,
Terri
Feline Healthcare Expert
Expert in feline health and behavior. 20 years experience with cats.