Floor joist or ceiling joist? Floor joist have a board on the end all the way along the side of the building called a rim joist. Like the cross bar on the top of a T.

Ceiling joist are nailed down into the top plate of the wall and to the rafters where possible.

A joist is a beam, a supporting structure in a building. The roof joist was riddled with dry rot and had to be replaced.

it depen on the size of the joist

A 20 delta size nail should be used to attach the band joist to a joist when end nailing. A 16 D can also be used.

There are several ways, but probably the easiest way would be to temporarily buck under the afflicted ceiling joist with a 2x6 temporarily, until the joist is in line with the others. Then go into the attic and cut and attach a 2x6 to the joist and vertically to the roof ridge. Remove the buck. The joist should stay in place.