Situation Kitniyot were cooked in a Passover utensil. 
Situation 1 The kitniyot's volume was less than 50\% of the volume of food cooked in that utensil. 
Status The food may be eaten and the utensil may be used on Passover (no need to kasher). 


Situation 2 The kitniyot's volume was more than 50\% of the volume of the food cooked in that utensil.
Status The food is not permitted to be eaten. 


Situation 2a The kitniyot's volume was more than 50\% of the volume of the food cooked in that utensil, and the total volume of the food cooked (kitniyot + non-kitniyot) was less than the normal volume of food which is cooked in that utensil.
Status The utensil may be used even without kashering, as long as you wait at least 24 hours after the utensil has been cleaned. 


Situation 2b The kitniyot's volume was more than 50\% of the volume of the utensil itself and more than 50\% of the normal volume of food cooked in it.
Status You may not eat the food (until after Passover) and must kasher the utensil after waiting 24 hours. 
NOTE You may only kasher a utensil on chol ha'moed but NOT on the festival days themselves.