Sorry but I beg to differ from other responders.
I am concerned about what maybe a continuance of the crack, I have ringed what concerns me in red in the attached.
The crack, both obvious and possible, seems to remove support from the arm pivot, circled in blue.
As the pivot is probably a stressed area any weaken of its support may lead to a failure in the future.
Aside from that, any attempts to glue this will probably leave traces and invalidate warranty. Likewise opening the shell to facilitate any DIY repair.
Further, I would be concerned about whether the glue of a 'glue job' will provide a good bond, perhaps those suggesting a glue job could give the name of a suitable, UK available, glue. (OP seems to be in Sheffield UK)
If you have care refresh then I would use it.
If you are concerned about warranty then I would not attempt a DIY repair and I would check, in writing/type, with DJI for an agent who can provide repairs that will not invalidate the warranty.
PS
I presume you have landing extenders fitted, best check if, with regards to repairs, their presence on a to be repaired drone, might create any problems for DJI and or their agents.