How will I be able to remove [NSNull Null] objects from NSMutableArray?

You can use NSMutableArray's removeObjectIdenticalTo: method, as follows

[mutArrSkills removeObjectIdenticalTo:[NSNull null]];

to remove the null values. No need to iterate.

removeObjectIdenticalTo:

Removes all occurrences of a given object in the array.

Discussion This method uses the indexOfObjectIdenticalTo: method to locate matches and then removes them by using removeObjectAtIndex:. Thus, matches are determined using object addresses. If the array does not contain anObject, the method has no effect (although it does incur the overhead of searching the contents).

You can try doing this,

NSNull *nullValue = [NSNull null]; 

[mutArrSkills removeObjectIdenticalTo:nullValue];

I hope this helps.