Leg pain after butt implants?

It is very difficult to determine the exact size and shape implant you will require to best match your ideal butt image without an examination by a board certified plastic surgeon. Not just any board certified plastic surgeon, but one with many years of frequently performing breast augmentation surgery including different approaches, techniques and implant choices. This is because several measurements not to mention your breast characteristics are needed to determine the optimal implant size to obtain your goals. Without knowing these dimensions it would be difficult to make this determination. For example, the existing base width of your buttock will determine, in many cases, the maximal volume per implant profile that you can accommodate. Liposuction of your lower back and fat transfer is also helpful as an adjunct to implants. Using “want to be” photos however are useful if simply provided to the surgeon.

at this point of your recovery pain is still normal but should not persist for more than 3 weeks post op.  be sure to contact your implanting surgeon for any questions or concerns to ensure a speedy and smooth recovery. Be sure to choose a board certified plastic surgeon who specializes in this procedure and is well known in the medical community for it.  Ask to see a photo gallery and patient testimonials.

Leg pain after butt implant augmentation is a not so infrequent side effect as the implant can place pressure on the sciatic nerve; This usually resolves completely by 3 to 6 months at the latest.

Thank you for your question. Some degree of pain is still acceptable in the first week following buttock augmentation with implants. But I would suggest bringing it under the attention of your surgeon, so that they can guide you on the appropriate further investigation and management to ensure that what you are feeling is considered normal in terms of your post op course. 
In my practice I would have a patient come in, examine the buttock area to ensure the implant is still positioned correcty and not shifted resulting in pain. If your scar is also healing well, it is not a definite but along with your observation that there is no excessive swelling it doesn't sound that there might be any infection at play.  Like I mentioned before, it is best that these be confirmed with your treating surgeon.
From a pain relief point of view, I would usually prescribe patients a longer acting anti-inflammatory to take twice a day and advise to take paracetamol during the day (Tylenol in the US) if they are returning to work. I also occasionally refer my patients to the physiotherapist post surgery, especially those that need to be back where they were as quick as they can be but do so safely. I hope your discomfort settles soon and you start enjoying your result! All the best.