To feel pain
undergo, experience, ache, smart, be in pain, be wounded, agonize, grieve, be racked, be convulsed, languish, droop, flag, sicken, endure torture, get it in the neck, look green about the gills*, complain of, be affected with, go hard with, flinch at, not feel like anything, labor under; see also hurt 4.
Antonyms recover*, be relieved, be restored.