Its an absolutely normal blood report.
Blood count as WBC 5.1 means there are approx. 5100 cells per cubic mm.( the norma is 4000- 12000). so,the wbc counts of your son is normal u don't have to worry much.
You son's Haematocrit is 0.373 which is also within normal range. The hct denotes about the haemaglobin concentration in the blood.
Lymphocytes seems to decrese slightly but nothing to worry much.
the question of joint pain seems to have the attention as rheunatic fever also presents like this.
if still have any doubt you can ask me..
the lymphocytes has come down , its true but what about the neutrophils?
Is neutrophils normal or decrease or increased?
has he taken any antibiotics yet?
The antibiotics do have impact on the blood counts. the antibiotics alter the normal blood counts of a person decreasing the lymphocytes.
As you told he was on antibiotics, now when you stop antibiotics for the ear infection then his counts will become normal again in the next few weeks.
You can just repeat the blood counts after a month, then it will come to be normal if no infection is present with him.
If still have any doubt left then you can asjk me.