High lymphocytes (51%, 2600), low neutrophils (41%, 2100).should i be concerned?

% vs abs: A complete blood count w differential counts not only the total number of white blood cells (wbc), but also the absolute # (abs)of the different types of wbc, & the % of the total wbc each type makes up. It is therefore possible to have a normal number but an abnormal %. Not necessarily sign of disease, but what it means depends on reason checked, your med history, what usual is for you, etc.

Depends: Are you ill? If not , I'd repeat the test in a couple of months to be sure since this may well be from an acute viral infection. If you are ill and this has been a persistent findings, then you'd consider seeing a hematologist