Hello,
Thanks for posting your query.
There are normally two below knee indentations due to the anatomy of the muscles and the knee joint . I assume that you are referring to the recently noticed prominence of the same which could be due to the workouts and nothing serious.
However if you have noticed visible swelling or fullness which can be indented with fingers on applying pressure then it is more likely to be the beginning of a muscle overuse injury.Still I consider it less likely because you mention that there is no pain or limitation of movement involved.
What happens when we start exercising a particular part of our body is that the muscles undergo considerable stress and if the technique is improper or the warm up/ stretching exercises are skipped then the muscles can get overuse damage resulting in swelling , pain etc.Occasionally repeated friction or movement can cause ligament and soft tissue inflammation too( eg bursitis ) which is very common around knee joint . This too can present with pain, swelling ,restriction of movement etc.

So as of now nothing seems worrisome however it's advisable to keep a watchful eye on the region for ruling out any progression of symptoms.
In case the indentations persist without any increase in size, pain , restriction etc then it could be the normal anatomical appearance itself , of your lower limb .
But if you develop new symptoms it's advisable to consult your doctor / orthopedic surgeon for further evaluation, confirmation of diagnosis and management .
Meanwhile make sure you give your muscles enough warm up and relaxation time along with work out time.
Remember ,many problems with the knee can be avoided by not making sudden increases in your training regime or drastic changes in bike set-up.

Hope I have answered your query.
I'll be available for any follow up queries.
Regards .

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