There are a few ways to progress past this and really integrate your interval skills with the rest of your musical life:
1. Actively practise using intervals for the musical tasks you want to accomplish.
For example, if you want to play melodies by ear using your interval skills, spend some time explicitly trying to use intervals to work out melodies by ear.
You can practice in a simple way just by sitting down, listening to a melody, and then trying to work out the notes by figuring out each interval in turn. It’s slightly laborious, but doing it bit-by-bit using intervals like this will gradually internalise that way of hearing and it will start to flow and come instinctively.
If you want to make things a bit easier on yourself you could use the “Step and a Half” iOS app which generates melodies and challenges you to work out the intervals used.
Actively, intentionally using intervals in this way is essential to really see benefit from them in practical skills li