Additional Study Information: This study will utilize an investigational drug combination (also known as the study drugs) called relatlimab and nivolumab as a possible treatment for recurrent/relapsed (returned) or refractory (treatment-resistant) cHL and NHL. An investigational drug combination is one that has not been approved by regulatory agencies, such as the United States (US) Food and Drug Administration (FDA), European Union (EU) European Medicines Agency (EMA), or others. The purpose of this study is to learn about the safety and effectiveness of nivolumab and relatlimab in participants with recurrent/relapsed or refractory classical Hodgkin lymphoma (cHL) or Non-Hodgkinlymphoma (NHL). The rationale for combining relatlimab with nivolumab is because it works in different ways to prevent cancer cells from escaping the immune system. There are 2 main parts to this study. In Part A, different doses of relatlimab and nivolumab will be given together to make sure that the study drug combination is safe and well tolerated in participants with cHL and NHL. In Part B, participants will receive nivolumab and relatlimab at the dose that was chosen from Part A. Part B will look at the effectiveness of the study drug combination in participants with recurrent/relapsed or refractory cHL and NHL. We are only recruiting participants for Part B of the study.