D.M.
My son had the same issue, and when I asked the doctor about a 'helmet', he looked at me funny...not kidding, he looked at me like I was an alien. He told me that helmets at that age would not teach him that he needed to pay attention to where he was going, or how manuver around corners and edges that were painful. My son's Pedi recommended padding corners on tables, and keeping a close eye on where he was in the house. Also, he recommended using baby gates to keep him in areas I felt secure in him learning to walk on his own while I was doing things around the house.
It made sense to me once I thought about it. Also, my son's doctor said that helmets are only used for kids who have equilibrium issues or really need them for safety. If you have questions or concerns talk to your son's doctor and ask if he/she thinks a helmet would be proactive to help you little one stay safe.
Good Luck!