Is it permissible not to wash or wipe the face and not to rinse the nose (Istinshaq) during Wudu (ablution) or Tayammum (dry ablution) if doing so continuously causes sinusitis that necessitates treatment with injections, especially in a cold country with limited financial means for heating?

It is from God's mercy upon His servants that the religion is ease, and the burden of worship is according to one's capacity. Among these provisions is the legislation of tayammum for those unable to use water due to harm or its unavailability. If there is harm from using water, the person performing ablution should wash the parts of the body that will not be harmed by washing, then perform tayammum for the face, and delay the tayammum for the ailing limb until after completing the ablution.