Kudos to DBradD.
His suggestion that you seek the opinion of a physician before you try makiwara training is valid.
My best friend, a retired Captain in the California State Police, and at one time Ronald Reagan's bodyguard studied the hard Korean martial arts for twenty years.
He trained daily during that time, and used the makiwara regularly. His hands became very tough and calloused. He had no problems with the flexibility of his hands until he passed forty five years of age. Since that time his hands have caused him constant pain and he has have developed arthritis in all the joints of his fingers, including the wrist. He no longer can type, nor can he grasp common household tools.
Of course there may be no relationship between his training and his present problems. But his physician theorized that hitting of the makiwara the knuckle pushups and the fingertip exercises did irreparable damage to his hands.
The irony is that he never had to use his arts in his profession.
Deathrow: Not a Doctor or a Martial Artist, just an old guy with good hands.