This is the 12696th most frequent Spanish word.
nomas
"Nomás" means "just," "only," or "no more" depending on context.
In this sentence, "nomás" (just) expresses a lack of additional reasons, implying his sole reason is his desire.
El dijo que no asistiría al evento, nomás porque no quería.
He said he wouldn't attend the event, just because he didn't want to.
Here, "nomás" (only) emphasizes the limited availability of restaurant spots.
Nomás queda un lugar disponible en el restaurante.
Only one spot remains available at the restaurant.
In this context, "nomás" (just) acts as a mitigating adverb for the following imperative verb.