Just got a used cot and it also came with a mattress which still very firm but not sure how it has been used? My partner said im worrying too much but I am about to buy a new one for 30£ because I don't feel comfortable with using the second hand mattress! I covered it with a protector and bedsheet.. will he be ok in it for one night? I need to collect the new mattress tomorrow from argos or can i keep the second hand one and just leave the protector on it?