I would contact the airline you are travelling with to get their advice. Usually companies ask for 6 months from the date you get back

We had a similar issue when the dog decided to chew our passports at the corners , Our travel agent said there were fine, the passport agency said they would need replacing so we took them along to Manchester airport and asked the check in staff, a very friendly Servisair lady took our passports to her manger who said they were fine and not to worry but to maybe put covers on them to stop them getting any worse.

Welcome to the forums.

According to the Foreign & Commonwealth Office Travel Advice for Tunisia, you should have at least 3 months validity on your passport for entry to the country.

However, as you have obviously experienced, some other travel websites and tour operators stipulate that you should have 6 months validity. Tour operators and airlines sometimes set their own passport validity requirements as part of booking conditions, irrespective of entry requirements for the country concerned. I think you perhaps need to speak to your operator and ask if the 6 months which they specify is advisory or mandatory, and whether it will be enforced at check in.

David