Hi,
Welcome to ehealthforum.
The pain and swelling could suggest possibility of infection. Is there any foul smell, redness, discharge associated? If yes then they too would indicate that infection is present and that you should not delay in taking medical attention.
Talk to your Mom, she will understand. It is not abnormal for anyone to masturbate at your age. Visit your gynecologist/healthcare provider for an examination and tests to see the extent of problem and identify what has exactly happened. Based on the results of examination and tests, treatment will be given to you.
Take care.