Nwakamma hit two free throws to give the lead back to the Hawks, 38-37 with 5:55 remaining, after New Hampshire had rallied from an 11-point deficit early in the second half.
Just under a minute later, two free throws by Sikma gave Hartford (15-12, 8-6) the lead for good after the Wildcats (7-18, 3-10) had regained a one-point advantage.
Nwakamma hit four free throws in the final 11 seconds to secure the victory.
Chandler Rhoads scored 16 points for New Hampshire, whose only lower output this season was a 51-40 loss to Hartford on Jan. 24
The teams combined to shoot 22 percent (11 of 50) in the first half, which ended with Hartford leading 18-12. New Hampshire made just 4 of 22 shots (18.2 percent).