How can I treat the lump on my gum above a crown I have?

The lump isn't painful but feels weird when I touch it. I'm sure it's on the tooth root. I went to the dentist regarding this and the lady told me to come back if it doesn't go away. It's a hard lump and isn't causing me any problems. She did mention a shadow on the x-ray that was taken. I feel not enough is being done and i just want to get it sorted quickly so it doesn't turn in to anything serious if it hasn't done already. Occasionally the tooth throbs, but again the throb isn't painful.