Chicken Tikka Masala is generally spicy, but you can control the amount of spice in the dish with how much cayenne pepper you add. I would recommend about 1/2 teaspoon if you like things a little milder and then work your way up from there a 1/2 teaspoon at a time. Remember that the heat will build, so if you have leftovers, they're likely going to be hotter than when you first made the dish.