Qenya
nasse
noun. thorn, spike, spike, thorn
ná-
verb. to be
ye-
verb. to be
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.
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.
A noun for “thorn, spike” in The Etymologies of the 1930s under the root ᴹ√NAS “point, sharp end” (Ety/NAS).
Neo-Quenya: For purposes of Neo-Quenya I would use this word for “spike”, but for “thorn” I would use other words like [ᴹQ.] ecco or necel.