Al chile is a classic piece of Mexican slang that means "honestly," "for real," or "to tell you the truth." Its literal translation is "to the chili pepper," which makes it a fun and memorable phrase to learn.
In the song, Peso Pluma sings, "Pero, al chile, sí me dolió" (But, honestly, it did hurt me). He's using this very informal, conversational phrase to admit his true feelings after a breakup, making the raw emotion of the lyric feel more authentic and direct.
Peso Pluma gives us the ultimate breakup send-off in this modern corrido tumbado track. He is stuck in that messy in-between phase of moving on: he admits he still thinks of his ex's facial expressions when he runs into someone else ("Sigo pensando en tus gestos cuando se me cruza otra" [I keep thinking of your expressions when I run into another girl]), but he refuses to look back. Instead, he deals with the split by smoking, drinking wine, and distracting himself with "princesas" (princesses / other girls). He lays his pride bare with Mexican slang, bluntly confessing that "al chile, sí me dolió" ([to be completely honest / brutally real, it really hurt]).
Even while admitting the pain, he knows staying together was bad news: "estar contigo ya no me convino" ([being with you didn't suit me anymore]). He drops another great piece of casual Mexican slang, "la neta" ([the truth / honestly]), to make it clear that her kisses do not matter to him now ("a mí tus besos ya no me interesan" [and your kisses don't interest me anymore]). It is an honest, bittersweet tune about accepting that the love ended, taking your hits, and simply telling an ex, "bye."