not an expert here but i'm going to say no because it just means he probably swallowed some of the blood from his nosebleed and depending how much blood he swallowed it may have made him nauseated.
should i be concerned that my child vomited blood and mucus after a nosebleed? . she then broke into a cold sweat and passed out for a few seconds. this was the first time she has had a nose bleed.