Looks like the band or ceil is rotting, or it could be a header rotting if there is or was a window below. You really do need to get under there and check it out, it isn't going to get better on its own.
Floor dropping
Hi, recently I noticed that 2 areas on my first floor seem to be dropping, causing the floor to be uneven. Both areas happen to be above old basement windows that have been covered by brick and concrete before I moved in. I live in an old home in South Philadelphia, and have attached a picture of the floor...any insight on what might be causing this, or what I can do to correct it? Thank you in advance for any feedback.
