Hueles a viejo literally translates to "you smell old." While it might sound harsh, it's a very evocative and somewhat rare phrase to find in song lyrics, making it memorable.
In the context of the song, it's a poignant and direct way to express the feeling of aging and the passage of time. It's not just about a literal smell, but a metaphorical sense of being worn out, having many experiences, and facing the consequences of time, especially when reflecting on past loves and missed opportunities.
This song paints a picture of someone looking back on a life full of struggle. The lyrics describe a person who has been through a lot, like being "soaked in this winter," and has spent a long time away. They've learned the hard way that it's difficult to "change course." Life feels like a constant, tiring race, full of stumbling and chasing after things, yet they still have a desire to go out and "burn the world."
Despite this lingering ambition, the song's main idea is the difficult realization of getting older. The speaker finds it hard to accept that they now "smell old" and that the years have just "dumped" them in a certain place. There's a sense of regret and unfinished business, with "so many bills left to pay." The memory of a past love from "so many Januarys ago" only emphasizes how much time has passed, leaving them with the feeling that they were never really suited for happiness.