Hi Cath, Exercise can do 2 things strengthen muscles and reduce fat,the latter being subject to calorie control.The direct inner thigh is not a place for specific muscle at all so unwanted size would come from fat.The nearest big muscle group would be at the back of the thighs called 'Hamstrings' Going upstairs uses the thigh group, coming down use the hamstrings. You are already doing good exercise for these groups, but too much could bunch the muscle inside the leg. Therefore what are you looking at fat or muscle ? When your leg is in tension, muscle will be firm but fat always soft.
Excess cycling may shorten the muscle, if so you must incorporate exercises that concentrate on straightening the legs, no kinky knees!