Valley were quickly back to winning ways but they made hard work of it before a Liam Francis header settled matters eighteen minutes from the end of normal time.
Lewis Rankin had given Town a half-time advantage, but the hosts then failed to kill off their Leicester-based opponents and allowed them back in the game halfway through the second period by conceding an equaliser.
Rugby's starting line-up showed five changes from the weekend defeat at Northampton ON Chenecks, with new signing Edwin Ahenkorah making his debut, and Francis, Dom Perkins, Rankin and Justin Marsden all back in.
Nirvana's Nickesh Savjani's speculative strike curled just wide of the target in the opening minutes, but Valley soon settled into the game with the pace of new boy Ahenkorah and Charlie Evans starting to cause the visiting back-line difficulties.
Evans carved out a good opportunity for himself but then delayed too long and was unable to get a shot off, whilst Rankin saw his effort blocked in the box.
Francis headed Rankin's corner wide and Leicester keeper Michael Antkowiak denied Ahenkorah a debut goal at close quarters, whilst Richard Blythe was another Town man guilty of dallying on the ball in the box after Ahenkorah had done well to get in behind the Nirvana defence.
Rankin did break the deadlock however on 35 minutes with an exquisite left-footed finish into the top corner after he had cut in from the right hand side following Blythe's pass out to him.
The opening goalscorer nearly repeated the act shortly after, but this time his strike was deflected away for a corner.
Evans had two decent chances to double the advantage ahead of the interval, when first he directed his shot straight at Antkowiak after he burst through the middle and then he headed Keenah Rosser's cross over the bar from close range.
The second half saw an uneventful start, although Francis nearly added a decisive contact to a Rankin set-piece that Antkowiak could only get a hand to.
Both sides continued to struggle to create much of note, although the visitors were looking to threaten on the counter and their reward came when Jordan Nelson broke clear to fire one low past Matt Hill to level things up on 69 minutes.
The state of parity was short-lived though, when Francis met Josh Steele's deep delivery with a looping header that Antkowiak was just unable to prevent finding the net.
Town survived the remaining minutes with relative ease, with the only real opportunity thereafter coming their way when sub Harry Holloway's effort on the turn was blocked.
Line-up: Hill; Rosser, Steele, Recci, Francis; Perkins, Blythe, Marsden (Holloway); Evans, Rankin, Ahenkorah. Subs not used: Kavanagh, Tulloch, Adams, Koriya. Booked: Recci, Perkins.
Nirvana line-up: Antkowiak, Gore, Bains, Calver, Gerald, Poulton, Anastasi, Savjani, Nassor, Nelson, Cisse. Subs: Gonga, S.Master, D.Master, Patel, Wingfield.