You absolutely must talk to the airline. Buying an A-B-C ticket and flying A-B is called hidden city ticketing and airlines generally frown at it and most definitely do not allow normally to claim luggage in B. In fact, your ticket is A-C with B just being a coincidence. If there is a problem the airline has absolutely every right to route you through A-D-C or even A-D-E-C as the contract between the airline and you is for A-C and nothing else (although in this case you will likely be late and there might some compensation due to that but that's an aside).
The reason here is that it's not unheard of to A-B-C be cheaper than A-B alone! Flights are not priced by distance or number of connections, they are priced by supply and demand. So perhaps there's a competitor which flies A-C direct but this airline wants to undercut it so they will sell A-B-C for cheaper -- but B in this case is a hub and A-B very well might only be served by this airline and so it might be more expensive than A-B-C.