There is no answer in the code. Just make sure the weld is clean and weld it. You may wish to do some volumetric NDE to verify the weld is still acceptable.

There's no time limitation to complete the weld, provided, as js55 said, it's clean and free from rust, oil, grease etc. 
Back in my days of erector engineer always happened that, during the last piping inspection before hydro test, we discovered one uncomplete weld. Surely, at lunch or quitting time the bell rang and the welder hurried up his way to the exit gate. Then, when returning back to the job, he forgot about the uncomplete weld and started another one.
Giovanni S. Crisi
Sao Paulo - Brazil