Is it obligatory to conceal the pursuit of knowledge, and does disclosing it diminish its reward, or is it obligatory to disseminate it?

If your informing your friend that you are educated is for the purpose of cooperation and studying, then there is no harm in that, because it is a benefit, and studying knowledge is an act of worship. However, if the purpose is to show off one's honorable self and knowledge, then this is blameworthy, due to the Prophet (peace and blessings be upon him) saying: "Whoever seeks knowledge to compete with scholars, or to dispute with fools, or to attract people's attention to himself, Allah will admit him into the Fire." Spreading knowledge, acting upon it, and advising others is good as long as it adheres to Islamic guidelines.