I cheated will i gain weight?

Ive been on a diet for the past 3 and a half month! i already lost 22 pounds! went from 163 to 141! but saturday i ate half a pancake and today there was an open buffet at the graduation and i ate a few mini sandwiches! and a glass of champagne! Will this affect my diet? will i gain weight? i work out 3 to 4 days a week!