What Causes Cough And Cold In An Infant After Starting Solid Food?

I HAVE A BABY GIRL SHE S 5 MONTH OLD AND 2 WEEKS AND I GAVE HER JUST A LITTLE BIT OF MIXED CEREAL THIS AFTER. SHE HAS LIKE A LITTLE COLD BEEN COUGHING THE LAST FEW DAYS ANYWAYS THE POINT IS SHE S NOW VOMITING BUT ALL SHE VOMITS IS LIKE SOME WATER AND I WOULD REALLY LIKE TO KNOW WHAT TO DO