Hi, Since you have a known sinus trouble this is possible but at the same time it is worth to note that sinusitis would cause a large swelling and not just a line. - Local problems like sty, cyst can be the cause - Insect bites at the corner - If near inner canthus then it can be related to Dacryocystitis Hence I would advise you the following in such a situation. Consult your primary doctor first for preliminary examination and investigations to know the exact cause so that he can start the primary treatment and refer you to the proper specialist as per the findings (Say for example if the cause is sinus related then see en ENT surgeon). Get a C-T scan of sinuses and related investigations to get the proper diagnosis and thus get treated specifically (Say if the problem is related to eye condition then consult an ophthalmologist). Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. T. Chandrakant, General Surgeon