Mastitis presents not just as a lump, but as a larger area of breast that often appears pinker and warmer than the rest of the breast. It soon becomes very tender to the touch. Some women (BUT NOT ALL) will feel flu-like and develop a fever. Mastitis starts out as a blocked duct (which is what you probably have) that isn't cleared.
Warm compress, massage toward the nipple, pumping and drinking plenty of water should draw out the blocked duct. Once it clears, see if your doctor can write you a prescription or an electric pump. You can then pump you milk and give it to your 11 month old. You can even cook with it!
As for getting an 11 month old to return to the breast after months of being weaned, it unfortunately is highly unlikely that they will "remember" the mechanics of nursing at the boob. Nursing a breast is very different than the bottle. Whatever you do, don't force the breastfeeding issue with your child, or they can really be turned off to the breast.
You can try an SNS (Supplemental Nursing System) - this may help the child understand what milk comes from the nipple. You can also try a breast shield, which feels more like a bottle. But remember, just simply giving the child breastmilk is great, so don't too frustrated if it has to come in a bottle or sippy.
Best of luck!