Hi welcome to HCM .
Apart from Ptosis
and constricted pupil, did you notice any difference in sweating on that side of your body/ face? This symptom determines the level of lesion in Horner's syndrome and the investigations are done accordingly.
Since you are a known case of Lymphoma
, there is a chance of recurrence and compression causing Horner's Syndrome. Get a Chest X ray
done and a repeat CT to rule out apeass lesions. Treat the cause is the goal in Horner's .