If it's firm it should be fine. (Does that sound right?) It's been too long since I grew tuberous begonias, but I think most any bulb or tuber that's still firm will grow. It's amazing how co-operative plants can be--they really WANT to grow. Sometimes we get in their way--speaking for myself at least!

Place it in a bright room, hollow side up. I put mine on a bed of damp peat moss in a warm bright room. Do not bury it. No direct sunlight. too much dampness will result in rot. Wait for the pink buds to grow 1/2" and some white fleshy roots. Plant in a soil-less planting mix (from a garden store). They should ultimately be buried 1" deep.