Its almost impossible to give you good advice with just a pic of the corner. Please post another pic showing the whole patio and more of the garden. You could place a corner planter on the edge of the patio. It would need to be weighty though. Placing a planter or pots on the grass will kill it underneath unless that is not a problem? I would be inclined to get a small low fence just for the corner and drill some bolts into your paving to fix it. It could be removed when no longer required. Your patio could have had a curved corner to avoid this problem if it had been planned from the outset.

Perhaps put a nice large pot on the patio in the corner space. Something like an olive tree or acer would look nice. Corner would become less of trip hazard (something like the photo but positioned at the edge where corner is). Alternatively, plant some shrubs or flowers in the grass around the corner.

Or create a nice patio border around the corner

I would have a high planter that is on the grass and goes around the corner of the patio. This will create a fixed border between the patio and lawn and enclose that part of the patio and also link it to the lawn to create height and interest

Something like this but with the planer taller so it is about 2 feet above surface level of patio. Could be made of brick, wood, Cotten steel - it depends on your style if you like contemporary or traditional

I think a simple idea is to cut out a border in the grass and plant something there. Much easier than putting a planter on the grass which will be difficult to mow around and will need constant watering in dry weather. So cut out the border, lift the grass off, dig a little compost into the soil and plant away. My sister has a much higher patio and she has planted tall grasses there to act as a guide/barrier. However any shrub will do, maybe a Cistus which grows to 4’ but spreads about 6’ wide. It’s evergreen and has lovely white or pink flowers in summer. This is my one.