The Collaborative International Dictionary of English v.0.48:

Nubble \Nub"ble\, v. t. [Cf. LG. nubben to knock, cuff.]
   To beat or bruise with the fist. [Obs.] --Ainsworth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nubble
    n 1: a small lump or protuberance [syn: nub, nubble]