Hi Nabeel,
yes, there's a slight difference in meaning.
un peu d'argent -- a bit of money.
peu d'argent -- little money.
For example:
Il ne me faut qu'un peu d'argent pour ça. -- I only need a little bit of money for that.
Il est pauvre. Il a peu d'argent. -- He is poor. He is little money.
Hope that helps, -- Chris (not a native speaker).