Chimba is one of the most popular slang words from Maluma's home country of Colombia. While its meaning can be very flexible depending on the context, in this song he uses it to mean 'awesome' or 'the best'.
He proudly sings, "Pero una chimba ser Antioqueño" (But it's awesome to be from Antioquia), expressing deep pride for his roots. Learning this single word is a fantastic key to understanding the real, everyday language you'll hear in modern Latin music.
Maluma takes off the superstar mask here to talk straight about real homesickness. Leaving home to chase success sounds great until you are stuck far away, realizing time slipped by while you were gone. He pours out his heart to his mother ("Madrecita, ¿qué es esto que estoy sintiendo?" [Little mother, what is this that I am feeling?]) and admits he is hiding his tears so his grandmother won't worry. The whole track builds around one burning urge: "Solo dile que estoy loco por volver" (Just tell her I am crazy to come back).
He grounds that longing in Colombian pride, especially his home region of Antioquia. He drops the local slang term "parceros" (close friends or homies) when talking about hanging out on his old block, and gets hype shouting "Es un orgullo ser colombiano, pero una chimba ser Antioqueño" (It's an honor to be Colombian, but it's totally awesome to be from Antioquia—chimba is classic Colombian slang for something extraordinarily cool or great). By the end, he dedicates the message to the "pela'itos" (young kids) chasing their own goals, showing that returning home to his family, his neighborhood, and his real name, Juan Luis, matters more than any fame.