Hello Julia,
there are several points raised by your post.
The primary one, which is not really fodder for the beginning student of meditation, is that there are all sorts of obstacles belched up by the ego when one commits to the path (of meditation). Physical discomfort/pain can often just be another obstacle - like nodding off while sitting. The feet fall asleep, the knees ache, the head bobs, the mind flutters, the face itches…and it all emerges as so very critical that it must be dealt with immediately at all costs 
Stepping back from that, an asana practice which works abduction and external rotation of the hip (actually the femur or thigh bone) would be preparatory for Sukhasana and perhaps eventually for Padmasana. Such things can be addressed with your teacher since meditation is one of the foundational elements of a robust Yoga practice.
In the meantime, as someone else has mentioned, Virasana with a bolster or folded blanket(s) underneath the sitting bones might be easier. Or sitting on the front edge of a crossed bolster so that the pelvis tips forward.