How can I make my dish less sour?
There is really no way to reduce the acidity in a marinade or sauce without creating undesirable flavor compounds. Adding a base would neutralize the acid but would also produce salts which don't taste so good. 

If you are making a marinade then simply add less acid to it, however if you are using bottled sauce then you have a few options to deal with the excess acidity:


Add some water: thin the mix out, and you will reduce the acidity. You will reduce the overall level of flavor but at least it won't make the chicken too vinegary
Marinade using less sauce: Less sauce = less acidity
Marinade for less time: this will mean less acidity, but less penetration of the flavors into the chicken
Add some sweetener: this will not reduce the acidity but will balance it out


If it were me I'd combine some of the above, I'd add some sugar and maybe a bit of water until it's a bit weaker.