Leg pain after butt implants?

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.