Dont be nervous. They are built to take overly large meals. You may think its going to cause harm, but it won't. My SD tic ate some pretty big rats when i made a size switch, but he soon grew into the size and was just fine.
Dont worry about it. Its one thing feeding a snake a meal that cause the snake to be 5 or 6 times the girth it truly is. But feeding maybe 5% more than the 15-20% guide is fine. The rule isn't set in stone.