There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.

Gnomish

nag-

verb. to chew, gnaw

mal-

verb. to chew

A verb appearing as G. mal- “to chew” in the Gnomish Lexicon of the 1910s (GL/56), perhaps based on the early root ᴱ√MALA “crush” (QL/58).

Neo-Sindarin: The root became ᴹ√MBAL in The Etymologies of the 1930s (Ety/MBAL), whose Sindarin derivatives would start with bal- conflicting with later forms like S. bal- “✱to have [divine] power” (PE17/131). For purposes of Neo-Sindarin I would use ᴺS. nadh- “to chew, gnaw” from ᴹ√NYAD “gnaw” (Ety/NYAD).

nactha-

verb. bite

nanc

noun. bite

A noun appearing as G. nanc “a bite” in the Gnomish Lexicon of the 1910s (GL/59), clearly based on the early root ᴱ√NAKA “bite” (QL/64).

Neo-Sindarin: Since ᴹ√NAK “bite” appeared in Tolkien’s later writings, I’d retain the noun ᴺS. nanc “bite” for purposes of Neo-Sindarin.

Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.