Where’s the UN?
There is no UN military presence in Nigeria. This is a Nigerian issue to solve. The Nigerians have considered Boko Haram their fourth or fifth biggest security problem. Successionists in the Niger River Delta, Biafra, Urban unrest, etc, all have rated higher.
Boko Haram’s activities have been mostly contained in the Northeast, which has a smaller population. As long as they kept away from cities, the Nigerians were content to use second line troops as cannon fodder to contain them, keeping better and more reliable forces elsewhere. Well, now they are encroaching into the center of the country, maybe they’ll actually try and deal with them this time.