There should never be sharp pain in a joint in asana, ever. In muscle, yes there should be some discomfort or “pain” but in a joint, not ever. Additionally ligaments cannot be strengthened. Again, muscle can be strengthened but ligaments and tendons cannot.
If the aforementioned injection into the joint was cortisone that particular substance blocks pain receptors. It does not remove the pain. It merely prevents you from feeling it. That means the healing has not occurred AND it is incredibly easy to do recurring damage since there is no feedback to prevent it.
Very few things heal in two days. If the ankle “healed” in two days then you are blessed to have a super functional immune system. It is possible of course but it is not “common”.
As for padmasana, if it is painful then a response would be covered in the second chapter; 46th sutra of Patanjali’s work - sthira sukham asanam. The pose should be comfortable. Panoramix above offers direct guidance for following this; find a comfortable posture for the meditation practice and avoid padmasana.
In the meantime understand that most knee and ankle issues are physically tied to the hips. If you are not doing the Beginner’s Hip Opening Series then I suggest doing so twice a day. If you’ve already assessed and know your hips in the six of eight required movements then you may focus your attention on the ones that are more challenging for your body.