Immediately apply cooling elements (from the Gott) to the red spot, keep that up for about 12 hours. When an element gets warm, exchange it for a new cold one. Half an hour before nursing, apply a warm towel to stimulate the blood and milk circulation

Make sure the baby really empties your breasts.

What else can you do?

Start nursing with the healty breast, until the milk in the inflamed breast starts to flow. When you feel the milk coming immediately switch your baby to the inflamed breast. That way you make sure the baby uses the best sucking power at the sore breast, which has to be drank until it feels really empty. If necessary pump the healthy breast once he has drank enough.
Mastitis is not dangerous for your baby.

Go top bed, drink lots of water, tea or limonade. Ask grandma or a friend to help you out for a day or two. Take everyting you need (books, diapers, toys etc) with you in bed. That way you won't need to get up too often.

Get plenty of rest! 

If nursing doesn't go well with the inflamed breast, you need to pump. Get that breast as empty as you can. Use a warm towel to make it easier for the milk to flow before nursing. Apply the cooling elements again after nursing.

If all this doesn't help in a day or 2, contact your doctor to start antibiotics. (You do not have to stop nursing while using antibiotics)