Seeing "pending" on your NIN modification is not itself a bad sign. It means NIMC has your request and has not made a decision yet.
Here is what that status actually covers, how long is reasonable to wait, and when it is worth doing something about it.
What "pending" actually means
A pending request sits between submission and a decision. NIMC has not approved it, and has not rejected it either, so nothing has necessarily gone wrong.
This is different from a rejected request, which has already been decided against you, and different from an approved one, which has already updated your record. If your status shows different wording from these, that specific term is worth checking directly with NIMC, since we could not confirm a full published list of every status label the portal uses.
How long to wait before worrying
NIMC has said a modification typically takes 24 to 48 hours. Treat that as a rough guide rather than a fixed deadline, since it came from a spokesperson's comment rather than a published service standard.
Give your request at least that long before treating the wait as unusual. If you are well beyond it with no update at all, that is when it becomes reasonable to act rather than keep waiting quietly.
Checks to run yourself first
Confirm you are logged into the same account you submitted the request from, on the device and browser you registered with. NIMC's device rule can make your status look inconsistent if you check from somewhere else.
Check your email and any messages from NIMC for a request for more information you might have missed, since a pending status can sometimes be waiting on you rather than on NIMC.
When to contact NIMC directly
Once you are well past the stated timeline with no update and no request for more information, contact NIMC through the self-service portal's support channel rather than continuing to wait.
Have your submission date and any reference number ready when you do. That gives NIMC's support something concrete to check against, rather than a general enquiry.
What to avoid doing while you wait
Do not resubmit the same request on the assumption that a second copy will move faster. That risks NIMC holding two records of the same change, a more complicated problem to sort out than a slow first one, before you even consider a completely fresh NIN modification request.
Do not assume a pending status means a rejection is coming. Treat it as genuinely undecided until NIMC tells you otherwise.
If your request has already been decided against you, see what to do when NIMC rejects a NIN modification. For everything else, browse the NIN and NIMC hub.