I think that the safest thing to do, is to have this sudden big lump in your breast, evaluated by your physician.
What you have, could be a Cyst,or a Fibroadenoma (both benign lumps) or a breast infection (abscess) that needs to be treated.As you well know,one cannot be sure about the nature of any lump found in the breast,without proper investigation.
Please see your doctor without delay and hoping that it's nothing serious.
Take care and best wishes...
If you did not have the mass when you went to sleep, I guaranty you do not have a tumor, benign or otherwise.
You might have an infection. See your doctor.