ANSWER:
You must go and kiss her forehead and ask her for forgiveness while showing your guilt and remorse, otherwise Allah will be angry at you till the time your mother is sad or unhappy with you and nobody in this world can bear the Anger of Allah!
Never ever repeat such a sin again otherwise you would be paving your way straight to Hellfire, May Allah protect us all.
Make her happy, the way you made her cry and sincerely ask Allah for forgiveness!