The leaf curling could be due to overwatering or underwatering, transplant shock, and/or insufficient light. Avocado plants are not very tolerant of wet or poorly-drained soils so make sure the top inch or so of soil becomes fairly dry between thorough waterings. Push your finger down into the soil to check for moisture/dryness. Make sure the pot drains well (has a hole in the bottom) and doesn't sit in a saucer that holds water. Although over-watering is probably more common than under-watering, both can cause similar symptoms of wilting leaves, so it's best to feel the soil rather than watering on a schedule.

As a result of transplanting, there was likely some minor root damage (which impairs water uptake and can result in the wilting symptom). Again, monitoring your watering amount is important -- maintain even watering but not too much.

In addition, a sunny location in a cool room is best for avocado plants. Put your plant close to a window that gets as much light as possible without touching the glass.

Indoor air is often quite dry, and tropical plants like avocado appreciate humidity. It may help to aim for a level around 40-60% relative humidity. If needed, using a room humidifier can help and will be much more effective than misting or using a humidity tray. 

The avocado pit (seed) is no longer actually needed once the plant is rooted and has its own leaves to generate energy for growth. It would be normal for the seed to decompose gradually (it contained the embryo for the plant to develop and its job is done). 

Unfortunately, we don't have any avocado-specific growing tips for our area, as they are a novelty tropical plant and it can take a decade or more for them to reach fruiting age. Treated as a novelty houseplant though, try these tips for improving soil moisture/drainage, light, and humidity conditions.

Christa