Hi @kamommy, A dull bruise-like pain just under your left bottom rib is in the general area of the spleen. From my own experience, when my spleen was enlarged I felt a similar tenderness. Since your ache seems to be progressing it might not be a bad idea to schedule a visit with your PCP. They may suggest some blood work and also an ultrasound to check your spleen.
It may turn out to be nothing but there can be any number of health related that can cause an enlarged spleen from anemia, bacterial and viral infections, autoimmune or blood conditions. liver issues, etc..
If it’s bothering you enough to ask, it would be worth your peace of mind to have your doctor take a look, right? 😉