As you have already mentioned you have psoriasis
, these small lesions might possibly be due to exacerbation of psoriasis. These shower of rain drop like lesions also known as guttate psoriasis occur in cases of established psoriasis due to stress, fever, pregnancy
, drug induced, use of tar or withdrawal of steroids
etc. In dermatology diagnosis can only be made after seeing the lesions so it is necessary that you consult a dermatologist
for the same. Take care.