My brother just experienced a nosebleed accompanied by dizziness,, the nosebleeding stopped but he says he still feels strange. what is wrong?

Probably anxious: Sudden nosebleeds can be anxiety laden events especially if spontaneous, without provocation, & since it always appears much more blood is lost than actually happens many get nervous & may even feel sick or faint but not from blood loss- from the emotion of the event. Having said that, if your brother actually had a MAJOR nosebleed then, he should drink some fluids and rest. If no better see doc.