pang of conscience(feeling of shame, guilt, or embarrassment, resulting from behavior which one regrets) noun [UK: pæŋ əv ˈkɒn.ʃəns] [US: ˈpæŋ əv ˈkɑːn.ʃəns]
remorse(feeling of regret or sadness for doing wrong or sinning) noun [UK: rɪ.ˈmɔːs] [US: rə.ˈmɔːrs]