I just purchased a 60 yr old home. On the staircase going up to the 2nd floor the last oak tread in cracked with the grain but right in the middle. I cannot access from under and the tread is between two stringers.

I saw Tom Silva use a dowel system to repair a crack but mine is too far in for a dowel to reach.

What can I do to repair? If I can't repair and need to replace the tread how will I get a new one in? There are walls on both sides.